B1501

Step 1: Perform visual inspection of both left front and left rear turn signal bulb sockets for melted terminals, corrosion, water intrusion, or damaged pins. Remove bulbs and inspect for signs of overheating or socket damage.

Step 2: With ignition off and turn signal switch off, disconnect the BCM connector controlling the left turn signal output. Using a digital multimeter, measure voltage at the turn signal output wire at the BCM connector. Reading should be 0V; if battery voltage is present, the short is downstream of the BCM.

Step 3: If voltage present at BCM connector, disconnect left turn signal bulb sockets one at a time while monitoring voltage. When voltage drops to 0V, the last disconnected component contains or feeds the short. Inspect that circuit's wiring harness for damage, especially near body ground points and along frame rails.

Step 4: Using a multimeter in ohms mode with battery disconnected, test resistance between the left turn signal circuit wire and battery positive at multiple points along the harness. Resistance should be infinite (OL); low resistance indicates location of short to power.

Step 5: If no short found in wiring or sockets, test the multifunction switch by disconnecting it and measuring resistance between turn signal output terminal and power supply terminals with switch in off position. Should read infinite resistance.

Step 6: After repairs, reconnect all components, clear codes, and cycle the left turn signal on and off multiple times while monitoring with scan tool for code return. Verify proper flash rate and that BCM no longer detects voltage on circuit when off.